Activated-sludge processing apparatus and method for control of sludge to be returned

摘要

A part of effluent is taken out, saturated with oxygen in a dissolved oxygen-saturation tank 5, and transferred into a dissolved oxygen measurement tank 6. Also, a part of the activated sludge in an aeration tank 1 is extracted and transferred into the measurement tank 6 via a distribution tank 4, and the change of dissolved oxygen concentration in the measurement tank 6 is measured. Based on the result of measurement is determined an organic matter concentration in effluent, and an amount of activated sludge to be returned from a precipitation tank 2 to the aeration tank 1 is determined based on the organic matter concentration. Thus, the fluctuation of organic matter load in effluent can be monitored simply and the amount of activated sludge to be returned can be controlled to match the fluctuation. There are provided a method for enabling such an operation and an apparatus suitably used in the method.